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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 24 August 2010 by muoncounter

Guest post by muoncounter

By nature, science is a prediction business. We analyze what data we have available up to a given time and then we say: Here is what will happen if ... It is risky. The bad news is that everybody will pounce on our failures. So we need to look back every once in a while and celebrate one that was right.

In August 1981, Hansen, Johnson, Lacis, Lebedeff, Lee, Rind and Russell published a paper in Science entitled Climate impact of increasing atmospheric carbon dioxide, making the following predictions:

It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980s.

The predicted CO2 warming rises out of the 1sigma noise level in the 1980s and the 2sigma noise level in the 1990s (Fig 7). This is independent of the climate models equilibrium sensitivity for the range of the likely values, 1.4 to 5.6 deg C. Furthermore, it does not depend on the scenario for atmospheric CO2 growth, because the amounts of CO2 do not differ substantially until after 2000.

Nominal confidence in the CO2 theory will reach ~85 percent when the temperature rises through 1sigma and ~98 percent when it exceeds 2sigma.

The paper went on to forecast several effects of this warming:

Accelerated surface warming in the Arctic,

Global shifts in climate patterns (pronounced droughts in some areas and floods in others),

Longer agricultural seasons

The authors were somewhat hesitant to predict ice sheet melting and concomitant sea level rise, based on what they perceived was uncertainty in the thermal response time of large ice masses. However, they mention that Arctic melting will result in the opening of both Northwest and Northeast passages and a partially ice-free Arctic. This modest recommendation was made:

... the degree of warming will depend strongly on the energy growth rate and choice of fuels for the next century. Thus CO2 effects on climate may make full exploitation of coal resources undesirable. An appropriate strategy may be to encourage energy conservation and develop alternative energy sources, while using fossil fuels as necessary during the next few decades.

The following figure is the papers figure 7, shown with a plot of smoothed GISSTemp anomalies through 2010 as an overlay.

Note that the 1981 forecast was on the conservative side!

I attempted to recreate what was known at the time in the next figure, showing GISSTemp annual temperature anomalies through 1980. A straight line trend is used to form a trend line and an envelope for the noise.

In the final figure, this noise envelope is projected on the seasonal (summer and winter) GISSTemp record through July 2010.

It is clear that the warming trend predicted in the paper was already underway by 1980 -- and that is why the predicted warming of Hansen's Figure 7 was a conservative estimate.

Note: a subsequent Hansen paper (1988) was critically reviewed here. Much was made of the CO2 growth rate used in the models; 1.5 ppm per year seemed excessive at the time. The growth rate today is more than 2ppm per year. Guess we should have been paying closer attention.

Comments

O-o-o-o-K-k-k-k-k, so when we write up a 'basic' version of this, we need to explain what '1sigma' and 'temperature anomaly' mean. The latter in particular has a somewhat surprising technical sense, differing from the sense you would expect by combining 'temperature' and the usual meaning of 'anomaly'.

00

Response: Bit of "intermediate whiplash", I see, after all those Basic posts :-)

There's no plan to write basic versions of every blog post. We're only writing basic versions of the rebuttals of skeptic arguments. Fair point though, even intermediate posts should explain the technical terminology.

Thanks for the article, muoncounter. Every one of these "what did scientists predict decades ago" articles I read seems to tell the same story - climate scientists have generally underestimated temperature rise and potential climate impacts.

The question I would then ask - are the predictions now being published similarly conservative, or has the methodology changed to be more 'accurate'? It seems the IPCC AR4 predictions are conservative, which may be a cause for concern as authorities are basing long-term planning decisions on those predictions (particularly the sea level rise ones).

Bern, my impression is that the IPCC predictions are indeed conservative because of the requirement to reach consensus, which has the result that the most contrarian (philosophically and or economically) member nations force down the predictions so as not to frighten their own populations into asking questions about their policies.

Nice timing. Tom Fuller and others over at Bart's place are criticising Hansen for a supposed comment that he made about the West Side Highway being flooded today due to sea level rise in a Salon Magazine article. Fuller goes on to claim that Hansen has been discredited along with Dr. Mann.

Where is the scientific experiments and data proving the existance of the "Greenhouse gas effect" Hypotheses are fairy-tale until we see experimental data.
This paper is more circumstational evidence if its true.

00

Response:"Where is the scientific experiments and data proving the existance of the Greenhouse gas effect?"

The greenhouse effect has been directly measured for 50 years. Planes measuring the upward spectrum from 20km up find big "bites" taken out of outgoing radiation by greenhouse gases. This is confirmed by surface measurements that find corresponding extra radiation returning to Earth at those same greenhouse gas wavelengths:

the sigmas are the Standard deviation of the data. An envelope of plus/minus one one sigma includes most of the date +/- 2 sigma is almost all data. In Statistical process control, the term "six sigma" is used (from IBM) to denote the ultimate goal of SPC that application is the inverse of this application as instead of expanding your data pool, it narrows it, which means no variation in output test criteria. Climate researchers have been sounding the alarm for 60 years. If you look at the global temperature data, I can see the effects of both world wars (second more than first) as well as the great depression! That tells me that we humans do have an effect on global temps.

There's tons more material out there, factfinder - this post was the result of ~90 seconds with Google. It's based on >150 years of spectroscopy, radiation physics, repeated observations, etc. Read up and enjoy the science.

"This paper is more circumstational evidence"
Circumstantial? A model run 30 years ago made a prediction of current events that worked reasonably well. In my old business, that would be called a successful experiment (aka an oil and/or gas discovery) and we would be taking $$$ to the bank.

In my new (part-time) business, if I predict earth-surface cosmic ray counts based on 'space weather' observed by satellites, isn't that also a successful experiment? (no $$$ in muons, unfortunately). Why is climate science a field where people get called out whether they are right or wrong?

robhon - No, Spencer in that link is demonstrating the presence of backradiation with an (uncalibrated to atmospheric spectra) infra-red thermometer.

Spencer feels that cloud cover provides a negative feedback to global warming which minimizes the CO2 effect (something of a minority opinion), but he's well informed enough to speak clearly about how the greenhouse effect.

The 1981 paper underestimated warming to a moderate extent. This tends to contradict assertions from the contrarian cult that Hansen is some kind of "alarmist".

Regarding the 1988 Hansen paper, RealClimate has an update. Through 2009, the observed trend since projections started is 0.19 C per decade, vs 0.26 C per decade for Scenario B - a little behind but within margins of error. Hansen used 4.2 C for climate sensitivity. The climate sensitivity value for this model that best matches the observed trend is 3.4 C, with large error bars of course.

Annan has a recent post that looks at the 1988 model. While (as noted above) the model drifts a bit on the high side of observations (which Annan attributes to some combination of model characteristics of higher climate sensitivity, low thermal inertia, and lack of tropospheric aerosols), it has clearly demonstrated skill.

A triumphant title ("Home Run") may be warranted, but it may repel visitors who are undecided. Try this instead: "Global temperature has increased, as predicted by Hansen etal in 1981." Or: "... etal 29 years ago."

Interesting! But is it a good idea to check Hansen's predictions with his own GISS-data? The fact that GISS-data are so much higher than the other datasets makes me suspicious. What if you do the same analysis with HadCRUT or satellite data?

fydijkstra, what are you talking about? Over the past 30 years, the global (land/ocean) surface temperature increase in GISSTEMP is virtually identical to that from HADCRUT, NCDC, and the RSS satellite record -- they're all +0.16C/decade. The only major global temperature index that's noticeably lower is UAH, at +0.14.

The gray bars in Hansen's fig 7 are bounds on what temperatures would do if all climate variation was within 'the noise level of natural variation'. Temperature anomalies rose out of the noise in the mid-late 80's, as predicted.

Isn't that the real key? When a natural phenomenon rises out of its natural range of observations, its time to go looking, via modeling runs or whatever tools are available, for the causes.